For nearly 30 years, the first day of December has offered an opportunity to unite in the fight against HIV/AIDS and highlight how far we have come. Despite all the advances, girls and young women are still being left behind. That is unacceptable and must change.

Girls and young women are at particular risk for HIV infection. Around the world, nearly two million individuals over the age of 14 are infected with HIV every year. One in four of them are girls and young women between 15 and 24 years. In sub-Saharan Africa, 67 percent of new HIV infections among young people are in girls and women between those ages.

Why are young women at greater risk? Biology plays a part: they are physiologically more vulnerable to the sexual transmission of HIV than men their own age. But structural barriers such as gender inequality are also a major risk factor.

Take, for example, the situation of child brides. Gender inequality is at the heart of what drives child marriage. In low- and middle-income countries, one-third of all girls are married before they are 18, with one in nine married before the age of 15. That’s 15 million child brides every year.

These are girls like 14-year-old Jackline from Kenya, who lost both parents to AIDS. She had to leave school and marry a man 20 years her senior so she wouldn’t be a “burden” on her stepmother or neighbors. These girls often grow up without a decent shot at a happy, healthy, and productive future.

Child marriage has profound consequences for the health and well-being of adolescent girls and young women. Child brides are at greater risk of spousal or partner violence, and sexual or interpersonal violence is closely linked with an increased chance of acquiring HIV. Their husbands are also often older and have already been sexually active, which also increases the risk. In addition, it is very difficult for child brides to negotiate safe sex and condom use. The tragic consequence is that HIV infection rates in married adolescents are 50% higher than in their unmarried, sexually active peers.

We can change this seemingly hopeless situation by tackling the gender inequality that makes girls and young women particularly vulnerable to HIV infection. But it will mean that the HIV community must look beyond tests and pills, confront structural barriers, and work more closely across different issue areas.

We already know what works. Now we just need to take these programmes and actions to scale.

A perfect example is education. The longer a girl stays in secondary education, the less likely she is to marry as a child, the better her chances of employment are, and the less likely she is to become infected with HIV.

We need more HIV prevention initiatives and sexual and reproductive health services that support both married and unmarried adolescent girls. And things won’t improve unless we also engage boys, men, families, and communities to help promote gender equality and change long-standing norms about the role of girls and women in society.

If we are serious about ending AIDS, we need a broader view of the epidemic. We must focus on a more holistic approach that includes tackling the gender inequality that puts girls and young women at increased risk of HIV infection.

The HIV community can’t do this alone. Key actors in health, gender, education, justice, finance, and development must also play roles. At the 22nd International AIDS Conference (AIDS 2018) in Amsterdam next July, we will work together so that the programme offers practical ways to ensure that we are working across sectors for adolescent girls and young women.

If we can keep girls like Jackline in school, out of child marriage, and free of HIV, we will reap a triple dividend: healthier young people today, healthier adults in future years, and healthier parents for the next generation. And we will be creating societies that work for everyone.

This story was originally featured on Girls Not Brides.